The invention relates to a method of allocating computer addresses to units of a system for running an industrial installation, the units being interconnected via a local architecture for communicating time-shared digital information.
In known manner, the management of a system for running an industrial installation implies the presence of a communications architecture so that information can be transmitted between the various programmable operating units which are involved in the running of the installation in a manner that is well adapted to the various needs encountered.
In such systems, it is conventional to use time-shared operation of the transmission links between the programmable operating units, and to allow information that is subject to transmission constraints that are relatively flexible in terms of urgency to take advantage of the pauses that are left available on a more or less regular basis by other information that is subject to constraints that are more severe.
In the context of developments associated with computing, and in particular with communications networks of the Internet or the Intranet type, various techniques have been developed. These techniques make it easier to make use of stored information by making it available to a large number of parties, practically regardless of the location of the parties relative to the sites where the information is stored, and this is done in forms that are universally standardized.
The invention thus proposes to transpose some of those techniques so as to provide a simple and practical solution to a problem that exists in systems for running industrial installations where programmable operating units that are conventionally organized around respective suitably-programmed computers having associated memory, are interconnected by a local communications architecture.
As is known in this field, each unit has a hardware unit address which is physically defined and which is conventionally said to be xe2x80x9chard-wiredxe2x80x9d, which address serves to identify a particular unit amongst the others in the system and is conventionally imposed by the installer or by the operator when the system is put into service.
It is also necessary for the units which are to be able to communicate with one another by computer type information transmission techniques to have individual computer addresses enabling them to identify themselves when they send information and enabling them to be reached when information is sent to them.
Thus, when information is interchanged by using the Internet protocol IP, it is necessary for each unit to have an individual IP address. These addresses can be allocated in a local network in manual manner, however that solution is not entirely satisfactory, particularly when the number of interconnected units is high. This is often the case with local networks provided in industry, and furthermore it is sometimes necessary to modify such networks over time.
Addresses can also be allocated to units in a local network by means of an IP address server, such as BOOT P, which is provided in the Internet. However, that solution is not very suitable when the communications architecture involved does not enable a sufficient number of bytes to be transferred without segmentation, as happens in certain communications architectures for industrial systems.
The invention thus proposes a method of allocating computer addresses to units of a system for running an industrial installation, the units being interconnected by a local time-shared communications architecture in which information is transmitted in digital form, the method being applicable to units which are originally provided with a hardware address in digital form and which are suitable for communicating between one another by using the IP, TCP, and UDP protocols after each of them has obtained an IP computer address including a header made up of data relating to the network address of the local communications architecture followed by address data individual to the sending unit.
According to a characteristic of the invention, the allocation method provides for the following in succession:
an address request frame is broadcast over the local communications architecture by a requesting unit seeking to obtain its own computer address, said frame including in particular a destination UDP port address relating to one of the units acting as an address allocator in the local architecture, a source UDP port address specific to the requesting unit, and data characteristic of an address request;
the request is taken into account by an application in the allocation unit on said unit recognizing the UDP port address that belongs thereto;
an allocation frame having the same structure as the request frame is broadcast over the local communications architecture by the address allocation unit, said allocation frame including, in particular, the UDP port address of the requesting unit, at a destination level, and data corresponding to its own allocation unit IP address;
the data corresponding to the IP address of the allocation unit is taken into account by the requesting unit on recognizing its own UDP port address in the destination level of the broadcast allocation frame, and the requesting unit determines its own IP address for storage and operating purposes from the IP address data of the allocation unit that it has received, by substituting hardware address data specific to itself for the hardware address data of the allocation unit at the end of the IP address as communicated for said allocation unit.
The invention provides for the allocation and request frames to include in identical manner a header comprising in succession a physical address and a destination IP address which are characteristic of a broadcast, a source IP address relating to a source considered as being unknown in the context of a request frame and relating to the address allocation unit in the context of an allocation frame, a destination UDP port address relating to the allocation unit in the context of a request frame and to the address requesting unit in the context of an allocation frame, a source UDP port address relating to the requesting unit in the context of a request frame and relating to the address allocation unit in the context of an allocation frame, and a data byte characteristic of an address request in the context of a request frame and corresponding to the hardware address of the allocation unit in the context of an allocation frame.